Loudspeaker porting

ABSTRACT

In a loudspeaker system having eight drivers on a baffle, the baffle has two port openings centered in respective squares embracing respective groups of four drivers. A tubular column extender snaps into each port opening and has a snap cap for detachably securing a polyester disk over the opening. A grill formed with two openings for accomodating the column extenders covers the drivers. A grill retainer formed with openings at each end for accomodating the column extenders abuts the grill, and clinch nuts screws on the threaded end of ach column extender to keep the grill retainer against the grill with the grill against the front baffle.

BACKGROUND OF THE INVENTION

The present invention relates in general to loudspeaker porting and moreparticularly concerns a novel loudspeaker system having all theadvantages of the commercially available BOSE Model 800 loudspeakersystem while reproducing low frequency sound at significant sound levelswith reduced driving power with structure that is relatively free fromcomplexity through the use of damping material in the port tube that maybe readily changed with a structure that also helps keep the grill inplace over the loudspeaker drivers. The present invention incorporatesthe principles in application Ser. No. 719,949 entitled LOUDSPEAKERSYSTEM of Joseph Veranth filed Sept. 2, 1976, now U.S. Pat. No.4,146,744.

The present invention represents an advance over the commerciallyavailable BOSE 800 professional loudspeaker system that comprises eighthigh-compliance, full-range drivers connected in phase.

While that system performed well and reproduced sound at high soundlevels without audible distortion, the driving power required to producea given sound level in the bass frequency region was higher thandesired. The aforesaid pending application teaches using two reactiveair columns ports that function to reduce driver cone excursion at lowfrequencies and produce high output levels at deep bass frequencies withrelatively little distortion and reducing the Q of the port mass-cabinetcompliance resonance by placing damping material in each port tube.Although this invention works well, it was discovered that afterprolonged use, there was a buzzing sound during heavy bass passages. Itwas discovered that the cause of this problem was clogging of thedamping material. Accordingly, it is an important object of theinvention to provide methods and means for overcoming the problem notedabove.

It is a further object of the invention to achieve the preceding objectwith structure that facilitates maintaining a clean passage in the porttube damping means.

It is still a further object of the invention to achieve one or more ofthe preceding objects with structure that facilitates easy replacementof the damping means.

It is still a further object of the invention to achieve one or more ofthe preceding objects with structure that also helps detachably securethe grill to the baffle.

It is still another object of the invention to achieve one or more ofthe preceding objects with structure that may be readily assembled anddisassembled without tools.

It is still another object of the invention to achieve one or more ofthe preceding objects with structure that is free from undesiredsympathetic vibrations when reproducing sound at high levels.

It is still another object of the invention to achieve one or more ofthe preceding objects with attractive structure.

It is still another object of the invention to achieve one or more ofthe preceding objects with structure that is relatively easy andeconomical to manufacture.

SUMMARY OF THE INVENTION

According to the invention, in a loudspeaker system having a pluralityof high-compliance drivers in a common cabinet, port tube means having aport tube mass that resonates with the cabinet compliance, and dampingmeans in the port tube means for reducing the Q of the port tube massand cabinet compliance, the improvement comprises means for detachablysecuring the damping means in the port tube means to facilitatereplacement thereof when the damping means becomes clogged with dirt ordust. Preferably, the means for detachably securing includes a snap capthat snaps over an end of the port tube means for keeping the dampingmeans covering the port tube opening, the damping means typicallycomprising a polyester disk. Preferably the port tube snaps intoopenings formed in the baffle of the loudspeaker cabinet, a grill formedwith openings for accomodating the port tube means covers the baffle andis kept in place by means including grill retaining means formed with anopen region for accomodating the port tube means and fastening means,such as a clinch nut, secured to the end of the port tube means forurging the grill retaining means to contact the grill and keep the grillagainst the baffle. Preferably the port tube means comprises two porttubes symmetrically located in the baffle with each centeredsubstantially in a square embracing a respective group of drivers.

Numerous other features, objects and advantages of the invention willbecome apparent from the following specification when read in connectionwith the accompanying drawing in which:

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a perspective view of an embodiment of the invention;

FIGS. 2-7 are diagramatic representations of the steps involved inreplacing the damping means that also illustrate structural features ofthe invention; and

FIGS. 8-10 are side, end and half-sectional views respectively of a porttube.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

With reference now to the drawing and more particularly FIG. 1 thereof,there is shown a perspective view of an embodiment of the invention inwhich loudspeaker cabinet 11 comprises a baffle having four verticalangled facets 12,13,14 and 15, each having two drivers thereon. Porttubes 21 and 22 are centered between facets 12 and 13 and 14 and 15,respectively, the exposed end of each port tube being threaded foraccomodating clinch nuts 23 and 24, respectively, that abut the eyeportions of grill retainer 25 to keep the latter against grill 26.

Referring to FIGS. 2-7, there is shown a pictorial representationhelpful in understanding the steps involved in replacing the dampingmeans when clogged while illustrating various structural features. Thesame reference symbols identify corresponding elements throughout thedrawing.

Referring to FIG. 2, there is illustrated the step of removing theclinch nuts, such as 23. Referring to FIG. 3, there is illustrated thestep of removing the grill retainer 25. Referring to FIG. 4, there isshown the step of removing grill 26 which goes on baffle 31 and theeight nearly identical high compliance drivers such as described in U.S.Pat. No. 4,061,890 forming an upper row 32 and a lower row 33 with adriver in each row being on a respective one of the four facets 12-15.

Referring to FIG. 5, there is illustrated the step of removing port 21from opening 21A, port tube 22 already having been removed from opening22A. FIG. 5 also illustrates the structure of port tube 21 having snapcap 41 covering polyester disk 42 and a threaded end 43 foraccommodating clinch nut 23. Port tube 21 includes release tabs 44 and45 that may be pressed while pulling gently on port tube 21 to remove itfrom port tube opening 22A.

Diametrically opposed ridges, such as 46 have a front edge 46F thatengages the inside surface of baffle 31 to keep the port tube snapped inplace. Ridges 46 and release tabs 44 and 45 mate with the four radialnotches in space quadrature about openings 21A and 22A.

Referring to FIG. 6, there is shown the step of removing snap cap 41.

Referring to FIG. 7, there is shown polyester disk 42 removed. Theinside ends of port tubes 21 and 22 are preferably covered with gauzescrim 55 attached to port tube grill 51, and they may now be washed byswishing them around in warm soapy water, then rinsed in clear water andallowed to air-dry thoroughly.

The polyester disk 42 may then be replaced over the port tube end, snapcap 41 clamped over it to keep it in place as shown in FIG. 6. Porttubes 21 and 22 may then be snapped into openings 21A and 22A,respectively, by pushing firmly until they snap into place. Grill 26 maythen be positioned over port tubes 21 and 22 as shown in FIG. 4. Grillretainer 25 may then be positioned over port tubes 21 and 22 as shown inFIG. 3. Finally, clinch nuts 23 and 25 may be screwed to the ends ofport tubes 21 and 22, respectively, as shown in FIG. 2 to complete thereassembly of the system.

Referring to FIGS. 8-10, there are shown side, end and half-sectionalviews, respectively, of port tubes 21 and 22 helpful in betterunderstanding the structure. Port tubes 21 and 22 may be molded ofplastic material such as Borg Warner Grade DFA or equivalent. FIG. 8shows two complete threads 52 for receiving clinch nuts, such as 23 and24. The form of release tabs 44 and 45 is best seen in FIG. 10. Eachrelease tab includes a ridged surface 53 for gripping and is formed wtha notch 54 for engagement with the baffle. Preferably, scrim 55 isbonded to port tube grill 51 and is stiff black porous gauze-likematerial such as Solar Textiles No. HC434 that coacts with polyesterdisc 42 to provide a portion of the desired damping while alsoperforming a cosmetic function of presenting a black appearance to onelooking into a port tube that blends with the black external color ofthe assembled cabinet.

There has been described novel apparatus and techniques for facilitatingreplacement of the damping disk. It is evident that those skilled in theart may now make numerous uses and modifications of and departures fromthe specific embodiments described herein without departing from theinventive concepts. Consequently, the invention is to be construed asembracing each and every novel feature and novel combination of featurespresent in or possessed by the apparatus and techniques herein disclosedand limited solely by the spirit and scope of the appended claims.

What is claimed is:
 1. In a ported loudspeaker system having a cabinetwith a baffle plate supporting a plurality of high complianceloudspeaker drivers thereon with port tube means mounted in openingstherein and having a port tube mass for resonating with the cabinetcompliance and damping means in said port tube means for reducing the Qof the resonant system comprising the cabinet compliance and the porttube mass, the improvement comprising,means for detachably securing saiddamping means to said port tube means including snap cap meansdetachably securing said damping means over an end of said port tubemeans normally inside said cabinet, grill means adjacent said baffleplate for covering said loudspeaker drivers and formed with open areaaccommodating said port tube means, grill retaining means engaging saidgrill means to urge the latter towards said loudspeaker drivers coveredthereby and formed with an open area for accommodating said port tubemeans, and fastening means engaging the end of said port tube meansoutside said cabinet and for urging said grill retaining means towardsaid grill means.
 2. The improvement in accordance with claim 1 whereinsaid port tube means is formed with at least one threaded end and saidfastening means comprises a clinch nut for threadingly engaging saidthreaded end.
 3. The improvement in accordance with claim 2 wherein saidport tube means comprises first and second port tubes each formed with athreaded end,and said fastening means comprises first and second clinchnuts for threadingly engaging respective threaded ends of said first andsecond port tubes.